Soybean growers need to make production decisions that will provide positive impact to yield as well as avoid those that are not likely to impact yield.  Simply put, some management choices do indeed increase yield while others don’t.  As always, any producer of a crop commodity should spend the most effort and energy evaluating inputs that provide the greatest impact on yield and profitability.  NCSU Extension has evaluated many of these decisions and provided supporting data.  (The assumption is that these decisions involve timely planting.  If a timely planting date is not possible then some of the discussion that follows still applies yet other comments may not).

NC State University has analyzed soybean yield contest entries from the last 20 years to examine grower choices that tend to impact yield. These entries are from at least three consecutive acres of farmer production rather than small plot trials.   Such an extensive data base has revealed some detailed information and are outlined in the article, Key Management Strategies to Increase North Carolina Soybean Yield: What We Have Learned From 877 Soybean Yield Contest Entries.    Below are some highlights from this article.

Decision That Impact Soybean Yield

• Perhaps the most critical decision for high soybean yield is selecting the maturity group. Data consistently shows that soybeans from Group IV and Group V  yield higher than other timely planted soybean groups.  Should planting be delayed past about mid-May, later maturities may be more appropriate and yield slightly better, but this is not always the case.
• Planting date was listed as another critical factor. Increasingly NCSU data shows that early planted (in this area this relates to mid-April through mid-May) soybeans simply yield higher than those planted later.  Keep in mind that the range of planting dates within this study is April 2 through July 14^th.  The highest yield is 109 bu/ac and lowest is 28.  Again, this simply shows that the planting date has a great impact on potential yield.
• Use of a fungicide has shown to increase yield dramatically when planting a variety susceptible to common diseases, early planted soybeans, and when planting a Group IV or earlier soybean maturity group. Among contest entries, some yield advantage  over those that did not apply a fungicide seemed to be common, but relatively small.   However, one should also consider that other NCSU data shows that later planted soybeans, selection of maturity groups, varietal resistance, and timing of fungicide to be important factors as to whether or not the fungicide is beneficial to increase yield.
• A 7 bu/ac yield advantage exists among growers that planted 47 lbs./ac or less seed. Ideally, 70,000 plants/acre is the target for May and 90,000 plants/ac for June planting dates.  Not only is higher yield the usual trend, but reducing seeding rates decreases production cost to increase profit.
• Multiple herbicide application improved yield, especially if herbicide resistant weeds are a concern. A pre-emergence product coupled with a post-emergence, as example, provided an 8 bu/A yield advantage in the coastal plain compared to entries submitted with ≤1 herbicide application.
• Fungicidal seed treatment: In high-yielding situations in the coastal plain in which earlier-maturing varieties were used and foliar diseases were managed, a fungicidal seed treatment provided a 9 bu/A yield advantage.

Decision That Have Little to No Impact on Soybean Yield

• Row width had little impact on yield. Again, as just noted earlier, this assume a timely planting.  Should planting occur in mid-June or later, then utilizing narrow rows has been shown to increase yield.  However, when planted timely, row width has little impact on yield.
• Tillage does not really matter if nutrient and soil physical structure has been managed correctly. About half of the contest entrants were no-till and the other some sort of reduced or conventional tillage.  Despite comments from those promoting one system over the other, there is no long-term benefit of either tillage system.  During years of frequent rainfall, conventional tillage often performs best.  During years of drought, no-till production systems do best.
• Inoculating seeds did not consistently increase yield unless the field had not been in soybeans within the past 4-5 years. Having thusly said, even some NCSU data shows slight increases in yield resulting from seed inoculation.  However, it should be noted that increasing yield by inoculating seeds is not a consistent trend.
• Foliar insecticidal choice did not impact yield. Following integrated pest management using existing thresholds to treat when necessary affords profitable, high yielding soybeans.  However, the product used is not an indicator for potential high yield.  As such, use the least expensive product that will provide desired results.

This article is a short summary of the article, Key Management Strategies to Increase North Carolina Soybean Yield: What We Have Learned From 877 Soybean Yield Contest Entries, written by Rachel Vann, Jim Dunphy, Katherine Drake-Stowe, and Greg Buol.